It's not economic, as much as people like to believe.
Even socially democratic utopias like Norway ,which have such massive sovereign funds that their citizenry don't need to work a day in their lives, have a population birth crisis.
And while I obviously am not arguing against it, the biggest correlation with declining birth rates are education and women enfranchisement.
Honestly, a demographic implosion needs to happen with some generation. Better now, to reset capitalistic expectations of unsustainable growth then later when it's compounded.